Thanks Jono, will have another look. I have that crosser and was trying to shoehorn it into the first three words of the clue. Thanks for confirming the def.
Agreed, quite a challenge, despite cracking the central theme word early on. For me, 15a has all the hallmarks of a great clue: extremely brief, a totally plausible surface read, and an almost invisible definition.
Thank you Hamish for this and your Never give up on Rick Astley letter in today’s Guardian. Much appreciated by an Oldie who was not with it but still admired your very clever crossword ( and managed to finish).
Looks like today’s contribution from Paul is another tough one.